A 13-year-old otherwise healthy girl was diagnosed with Streptoccous pneumoniae endocarditis with involvement of the mitral valve and septic cerebral emboli. She underwent mitral valve replacement, and her immediate postoperative recovery was uncomplicated. A follow-up brain MRI revealed a 5-mm enhancing vascular lesion in the peripheral right frontal lobe. She was asymptomatic at the examination. Given her history, the lesion was highly suspicious for a mycotic aneurysm.
Mycotic or infected aneurysms are rare, accounting for < 1% of surgically treated aneurysms. Historically, they were most common following bacterial endocarditis. Currently, mycotic aneurysms often are related to intravenous drug use or immunosuppression. They may involve any artery, including the peripheral or cerebral vasculature. If cerebral, they are typically fusiform and peripherally located along the anterior circulation. They may enlarge rapidly and lead to fulminant sepsis or spontaneous hemorrhage with high mortality rates (~15%); therefore, early diagnosis is critical.1
CT and MR angiography with 3-D reconstructions are equally sensitive for the diagnosis and characterization of mycotic aneurysms. The aneurysms are contrast-enhancing vascular dilatations with flow voids on MR. Calcifications may be seen. Conventional cerebral angiography is helpful for treatment planning. Treatment options include endovascular embolization or open resection.2
In our case, angiography confirmed a single mycotic aneurysm arising from a branch of the orbitofrontal right middle cerebral artery without evidence of rupture. The aneurysm was clipped and resected without complication.
Acknowledgment: The authors would like to thank Melandee Brown, M.D., neurosurgeon, for her contributions to this case and manuscript.
At the Viewbox: Mycotic Aneurysm. J Am Osteopath Coll Radiol.